The term trailer as used herein refers to any form of towed vehicle, including an open tray trailer and a caravan.
Sway or oscillation of a trailer behind a vehicle is not an uncommon occurrence and can be a result of the actions of the driver, the condition of the road, other traffic, the weather or a combination of these or other factors. The results of an uncontrolled oscillation (commonly referred to fishtailing) can lead to serious damage to the trailer or vehicle and even to the occupants of the vehicle.
A variety of solutions have been proposed in order to resolve the problem of swaying movement of a trailer behind a vehicle. Some solutions involve controlled breaking of the trailer and other solutions involve devices for dampening the swaying movement. The present invention is directed to dampening swaying movement.
U.S. Pat. No. 6,283,489 to Hoog discloses an arrangement for reducing the sway of a trailer that is attached to a towing vehicle.
The arrangement comprises a towing beam that is disposed generally parallel to the bumper of a vehicle and has approximately the same length as the bumper. The towing beam includes a plate that extends from an extreme side of the beam, i.e. offset from a drawing arm of the trailer. The trailer is hitched to the beam by a towing arm that is modified to receive a first end of two extendible piston-type dampeners. The plate receives a second end of each piston-type dampener. Accordingly, any angular disposition of the trailer arm relative to the beam is resisted by the dampeners.
Although assisting to reduce sway of a trailer behind the vehicle, this arrangement suffers several draw backs.
The dampeners resist the extent to which the trailer can be angularly displaced relative to the vehicle in both horizontal and vertical directions.
In terms of restrictions on horizontal movement, this arrangement limits the extent to which the vehicle can turn around sharp corners and limits the manoeuvrability of the trailer relative to the vehicle. That is, the dampeners compress only to a certain extent at which point the dampeners form of rigid link between the vehicle and the arm of the trailer to prevent further angular displacement of the trailer relative to the vehicle. Any attempt to increase the angular displacement beyond this extent would result in destruction of the dampeners.
In terms of restrictions on vertical movement, the dampeners are fastened to the plate and the modified trailer by upright pins. While the pins permit the ends of the dampeners to pivot about a vertical axis of the pins, i.e. in a horizontal plane, the pins do not accommodate vertical angular movement of the vehicle relative to the trailer. Accordingly, the arrangement disclosed in Hoog does not account for pivoting the dampeners when the trailer is taken up a steep driveway, over a speed hump or down a boat ramp.
This arrangement also requires the dampeners to be attached either to the trailer or the vehicle each time the trailer is hitched to the vehicle. Similarly, the dampeners must be detached from the trailer or vehicle each time the trailer is unhitched from the vehicle. This is a nuisance when the trailer is frequently hitched and unhitched from the vehicle.
The dampeners in Hoog must be very stiff in order to resist movement of the trailer relative to the vehicle. However, if the dampeners are removed to enable unhitching of the trailer from the vehicle, the dampeners would be in a certain extended disposition. In order to refit the dampeners when hitching the trailer to the vehicle, the trailer must be disposed at the exact angular displacement relative to the vehicle when the dampeners were removed so the disposition of dampeners does not need adjustment to bridge the exact distance between the plate and the arm of the trailer. Alternatively, the disposition of the dampeners must be adjusted to bridge the exact distance between the plate and the arm of the trailer. In either case, this is a difficult task and makes the arrangement disclosed in Hoog difficult to use.
The arrangement disclosed in Hoog further requires a modification to be made to the vehicle and/or trailer to properly fit the arrangement and thereby have a sway-reducing effect. The need to modify the trailer and the vehicle contributes to an increased cost of using this arrangement. This is disincentive financially and modifications to the vehicle may be insightly.